25th IMRC Anniversary Lecture

Monday, August 15, 17:30 - 18:30

Prof. Hiroshi Amano

Hiroshi Amano received his BE, ME and DE degree in 1983, 1985 and 1989, respectively, from Nagoya University. From 1988 to 1992, he was a research associate at Nagoya University. In 1992, he moved to Meijo University, where he was an assistant professor, associate professor from 1998 till 2002, and professor from 2002 till 2010. He moved to Nagoya University, where he was a professor of Graduate School of Engineering from 2011 till 2015. On Oct. 1, 2015, he became a director of Center for Integrated Research of Future Electronics, Institute of Materials and Systems for Sustainability, Nagoya University. He has also been the director of the Akasaki Research Center (Akasaki Institute), Nagoya University since 2011.

During his doctoral program at the Nagoya University Graduate School of Engineering, he was able to realize high-quality epitaxially grown GaN film with metal-organic vapor phase epitaxy (MOVPE), p-type GaN filmdoped with Mg while conducting research with Professor Akasaki.For the first time in history, he established the technology necessary for the production of blue LEDs, thus performing a great achievement the development of the high-luminosity blue LED.

He is currently developing technologies for the fabrication of high-efficiency power semiconductor development and new energy-saving devices at Nagoya University. He has over 500 publications, and 30 patents. Prof. Amano shared the Nobel Prize in Physics 2014 with Prof. Isamu Akasaki and Prof. Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources"

Light-emitting diodes (LEDs) are considered to be the fourth generation of artifical lighting systems. Fire, which is based on the oxidation of
hydrocarbons, was the dominant light source for humans until the 19th Cenctury. The second generation was incandescent light bulbs which are based on
blackbody emission, so their mechanism can be explained by classical quantum theory. The third generation was fluorescent light bulbs. Their mechanism of
light emission is based on the transition of electrons, so they are actually a light source based on quantum theory. Unfortunately, a fragile vacuum glass
tube and Hg vapor are needed for fluorescent light bulbs. The principle of LEDs, the fourth generation of lighting systems, involves quantum-theory-based
energy trnsitions, and LEDs are composed of robust solid materials. Therefore, I believe that LEDs are one of the ultimate light sources for humans.

In 1962, red LEDs based on GaAsP were commercialized, and in 1974, green LEDs based on GaP:N were commercialized. In the 1970s, many researchers thought
that GaN-based blue LEDs would be the next LEDs to be commercialized. However, InGaN-based blue LEDs were next to be commercialized in 1993, 19 years after
the commercialization of GaP:N based green LEDs. Today, portable games machines and cellular or smart phones are very commonplace items, especially among
young people. Until the end of the 1990s, all the displays of portable game machines and cellular phones were monochrome. The younger generation can now
enjoy full-color portable games and cellular/smart phones because of the emergence of blue LEDs. In addition to their use in displays, blue LEDs are also
essential for realizing white LEDs. In combination with phosphors, blue LEDs can act as a white light source and are also used in general lighting. In
Japan, about three-quarters of general lighting systems composed of incandescent and fluorescent lamps will have been replaced with LED lamp systems by
2020, thereby reducing total electricity consumption by 7%, corresponding to a saving of 1 trillion yen per year.

The applications of group III nitride semiconductors are not limited to blue LEDs. AlGaN-based deep-UV LEDs are effective for the sterilization and
purification of water. UNICEF reported that 663 million people still cannot drink safe water, and 2.4 billion people do not use safe sanitation facilities.
New water sterilization and purification systems have been commercialized in which high-power DUV LEDs are installed. Other applications of DUV LEDs
include as a sterilizer for sanitation facilities, the curing of resins and inks, detecting forged banknotes, photolithography, and dermatology.

This material system is also promising for electron devices. In mobile or smart phone base stations, high-frequency RF amplifiers employing GaAs-based
heterojunction field-effect transistors (HFETs) are being replaced with those employing GaN-based HFETs because of their capability of higher-power
operation. By replacing Si-based power devices such as insulated gate bipolar transistors or super-junction MOSFETs with GaN-based power devices, the
average efficiency of inverters or converters can be improved from 95% to more than 99% in principle. As a result, we can expect an additional 9.8%
reduction of electricity consumption.

To realize a sustainable society and social resources based on nitride semiconductor devices and systems, we are facing several problems that must be
solved. In this presentation, I would like to discuss the current status of our understanding of nitride semiconductors, especially the problems to be
solved, and the prospects for their future application.

Lighting plays a major role in our quality of life. The development of light-emitting diodes (LEDs) has made more efficient light sources possible. Creating white light that can be used for lighting requires a combination of red, green, and blue light. Blue LEDs proved to be much more difficult to create than red and green diodes. During the 1980s and 1990s Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura successfully used the difficult-to-handle semiconductor gallium nitride to create efficient blue LEDs.